105a_ch03L6_L8_06

105a_ch03L6_L8_06 - Exam 1: Thurs. Sept. 14, 3:30-4:30 p.m....

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1 Exam 1: Thurs. Sept. 14, 3:30-4:30 p.m. ROOMS: A-G SGM 101 H-Z SGM 123 Bring a watch -- electronic devices are not allowed (cell phones, pagers, etc.) and the rooms do not have clocks. Bring your Casio FX-260. No other calculators are allowed. (Be sure to do your HW with this calculator so you know button locations and in which order to push the buttons, before the exam -- otherwise it could slow you down on your exam.) Bring your photo ID. Your ID will be checked during the exam. Bring a black pen. Pencils are not allowed. Do not use whiteout. Left-handed students have priority at the left-handed seats. The exam is 60 minutes, please arrive early, sit every-other-seat, and avoid sitting diagonally behind someone. No one may leave early. If you have special needs, please see Dr. Erickson ahead of time.
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2 L6:II. Stoichiometry (Chap 3) A. Relative atomic masses 1. Atomic mass units 2. Natural abundance 3. Mass spectrometer and the mass of an atom B. The mole 1. Rationale 2. Avogadro's number 3. definition of the mole 4. Sample problems 5. Formula mass C. Determining percent composition D. Determining empirical and molecular formulas E. Simple Chemical Equations 1. Definition 2. Balancing simple equations F. Stoichiometric calculations 1. Amounts of reactants and products 2. Limited reagent 3. Actual and theoretical yields Avogadro ' sn o . = 6.02214x10 23 molecules / mole Mass ( molecule ) = mol . wt .( gr / mole )/ N av ( molecules / mole )
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3 Chemical Stoichiometry Stoichiometry - The study of quantities of materials consumed and produced in chemical reactions. • The chemical engineer calls this " mass balances "
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4 Relative masses and atomic mass units Only relative masses can be inferred from Law of definite proportion Law of Multiple Proportions Avogadro's Law Example: Law of definite proportion says: H + O ⎯→ OH 1 g 8 g 9 g or 3 g 24 g 27 g
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5 Relative masses and atomic mass unit • Define mass scale: set m( 12 C) 12.00000000 atomic mass units (amu) Terrestrial natural abundance carbon: abundance mass (amu) •m ( 12 C) 98.89% 12.00000 ( 13 C) 1.11% 13.0034 naturally abundant C 98.89%(12.000) +1.11%(13.0034) 100% = 12.011 amu
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6 A scientist injecting a sample into a mass spectrometer. (right) Schematic diagram of a mass spectrometer. M + e - ⎯→ M + + 2 e - Atomic masses are measured in a mass spectrometer e ev B Deflection m
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7 From mass spectrometer: Determine mass in kg of 1 amu 12 26 26 27 mass( C) 1.99265 10 kg/atom 12.00 amu 1.99265 10 kg/atom 1 amu 12.000 amu/atom 1.66054 10 kg/amu × =
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8 Relative Mass Scales amu's or grams ? Microscopic scale: Atomic mass units: Mass of one carbon atom: Mass( 12 C) = 12.00000 amu Macroscopic scale Mass( 12 C) 12.00000 amu : Define a mole (quantity): 1 mole of 12 C weighs 12.000 g. One mole of carbon has the same number of atoms as one mole of sulfur, but how many atoms are in a mole?
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9 The Mole •The Mole is a counting unit: 1 dozen = 12 1 mole = 6.022137 x 10 23 •The mole is defined as the number of atoms in exactly 12 g of 12 C •The molar mass (atomic weight in g) is defined as the mass of one mole of that element Why isn't the molar mass of carbon exactly 12.000 g?
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105a_ch03L6_L8_06 - Exam 1: Thurs. Sept. 14, 3:30-4:30 p.m....

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